1. Field of the Invention
The present invention relates generally to a remote measuring system and more particularly to a system for measuring temperature and current at a remote point in the electrical distribution network.
2. Discussion of the Background
When electricity is produced at a central power plant, it is then transmitted to various consumers by way of step up transformers, tielines (interconnecting lines between two power systems), transmission lines, step down transformers, sub-transmission lines, high voltage primary distribution feeders and distribution transformers, and low voltage transmission lines. In the course of forming the network, it is necessary to have coupling points at a number of locations in order to link various parts of the network. These allow for simpler installation and connections to various parts of the electrical distribution system. However, resistance is present at each such coupling point. If the coupling point is not secured properly, the resistance at the coupling point will increase. This results in an increase of heat also. If the heat generated is greater than the power rating of the coupling point, it is possible for the coupling point to burn open and be damaged. Thus, the temperature of the coupling point is an indication that an insecure joint is present at the coupling point.
Further, it is important to separate the conductors from each other and other items in order to prevent any flow of electricity from the conductors to ground cables, circuit breakers and other lines. In order to prevent this, the various parts are supported or suspended on insulators. When a higher voltage is carried by a conductor, the thickness of the insulator needed to support it must also increase. It is likewise necessary to keep a minimum distance between the conductors and any other items in order to prevent an electrical discharge. For example, a transmission line carrying 10 Kv requires a minimum gap of 125 mm from the line to any cabinet that houses it. Otherwise an electrical discharge in the form of a spark can occur which results in a voltage collapse in the transmission system and a blackout in the network. Such a minimum gap must also be included between the various power lines due to the different phases of electrical power.
In view of this, it is desirable to include measurement equipment to determine if the temperature of various joints has increased and the current being carried by the conductors is appropriate. However, in a facility such as a power plant or substation, it is not feasible to install the necessary sensors since the use of conducting wires can be the cause of electrical discharge within the cabinet. The use of optical temperatures sensors or infrared temperature meters using optical fibers is also not justifiable. Unfortunately, the use of such optical equipment requires a battery and accordingly requires a replacement when batteries are used up. Further, fiber optics are brittle in nature and can easily be damaged. In addition, any device used must be able to withstand a very high operation voltage. As a result, optical devices are not preferred. Although a power trip can be detected by a Supervisory Control and Data Acquisition (SCADA) system installed in the power plant, the SCADA system cannot locate which coupling point causes the trip.
Accordingly, the need to have sensors for temperature and current at a coupling point is clear and yet existing systems have deficiencies, which are not desirable. These gaps between two sets of power lines or power lines and solid structures such as cabinet walls are very small. Such gaps are reduced further by power lines that are supported by additional insulators. Existing optical systems require batteries, or are brittle and have other problems. Further, it would be desirable to have a system which can remotely detect temperature and current at coupling points in an electrical network and which is easier to operate.